2022 SSMO Relay Round 4 Problems/Problem 1

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Problem

On any given day, there is a $70\%$ chance that a robot will find a new organism, a $20\%$ chance it will find an already discovered organism, and a $10\%$ chance that it will find nothing. Given that it has found a new organism, there is a $90\%$ chance it will correctly determine that it is a new organism, and given that it has found an already discovered organism, there is a $75\%$ chance that it will correctly determine that it has already been discovered. The expected number of days that the robot will take to report that it has found a new organism (regardless of whether it actually has) can be expressed as $\frac{m}{n},$ where $m$ and $n$ are relatively prime positive integers. Find $m+n.$

Solution